The present invention relates to a hand tool for applying a ferrule to a safety cable passing through a plurality of threaded fasteners to prevent the unintentional unthreading of such fasteners.
In rotary machinery having close tolerances between rotating and stationary elements, such as turbines, it is imperative that all objects, no matter how small, be kept from contact with the rotating elements of the machinery. The presence of any foreign object could result in the catastrophic failure of the entire machine.
Such machinery is inherently complex and requires many nuts, bolts, screws and other threaded fasteners to assemble all of its components. Since the operation of such machinery may involve very high rotating speeds, which may induce vibrations into the machine elements, it is necessary to provide some means for preventing the inadvertent unthreading of the numerous threaded fasteners.
It is known to apply lockwires to threaded fasteners to prevent their inadvertent unthreading. Typically, the lockwire passes through a transverse hole in at least two threaded fasteners and is twisted back on itself in alternating clockwise and counterclockwise directions between the threaded fasteners. The process is duplicated between additional threaded fasteners until the entire threaded fastener pattern has been safety wired. Following the required stringing and twisting, the wire is cut and bent into a certain position.
While the known lockwire technique has provided satisfactory results, it requires a very time consuming and laborious application process. Often the final result is unsatisfactory due to variations in the quantity and tautness of the twists, and the variations in the tension on the lock wire. It has been estimated that annual losses of approximately $10,000,000 are incurred just from re-working unacceptable lock wire assemblies.